package com.zipking.cloud.springbootmybatis.util.thread.threadPool;

import java.util.ArrayList;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.atomic.AtomicLong;

public class DefaultThreadPool<Job extends Runnable> implements ThreadPool<Job> {

    // 线程池最大限制数
    private static final int MAX_WORKER_NUMBERS = 10;
    // 线程池默认的数量
    private static final int DEFAULT_WORKER_NUMBERS = 5;
    // 线程池最小的数量
    private static final int MIN_WORKER_NUMBERS = 1;
    // 工作列表、插入执行的任务或者工作
    private final LinkedList<Job> jobs = new LinkedList<Job>();
    // 工作者列表
    private final List<Worker> workers = Collections.synchronizedList(new ArrayList<Worker>());
    // 工作者线程的数量
    private int workerNum = DEFAULT_WORKER_NUMBERS;
    // 线程编号生成
    private AtomicLong threadNum = new AtomicLong();

    public DefaultThreadPool(){
        initializeWorkers(DEFAULT_WORKER_NUMBERS);
    }

    public DefaultThreadPool(int num){
        workerNum = num > MAX_WORKER_NUMBERS ?
                MAX_WORKER_NUMBERS
                : num < MIN_WORKER_NUMBERS ? MIN_WORKER_NUMBERS : num;
        initializeWorkers(DEFAULT_WORKER_NUMBERS);
    }

    @Override
    public void execute(Job job) {
        if(job != null){
            // 添加一个工作并进行通知
            jobs.add(job);
            jobs.notify();
        }
    }

    @Override
    public void shutdown() {
        for(Worker worker : workers){
            worker.shutDown();
        }
    }

    @Override
    public void addWorkers(int num) {
        synchronized (jobs){
            // 限制新增的工作者不能大于最大值
            if(num + this.workerNum > MAX_WORKER_NUMBERS){
                num = MAX_WORKER_NUMBERS - this.workerNum;
            }

            initializeWorkers(num);
            this.workerNum += num;
        }
    }

    @Override
    public void removeWorker(int num) {
        synchronized (jobs){
            if(num >= this.workerNum){
                throw new IllegalArgumentException("beyond workNum");
            }

            // 按照给定的数量停止worker
            int count = 0;
            while (count < num){
                Worker worker = workers.get(num);
                if(workers.remove(worker)){
                    worker.shutDown();
                    count++;
                }
            }
            this.workerNum -= count;
        }
    }

    @Override
    public int getJobSize() {
        return jobs.size();
    }

    // 初始化工作者
    private void initializeWorkers(int num){
        for(int i = 0 ; i < num ; i++){
            Worker worker = new Worker();
            workers.add(worker);
            Thread thread = new Thread(worker, "ThreadPool-Worker-" + threadNum.incrementAndGet());
            thread.start();
        }
    }

    // 工作者、负责去消费任务
    class Worker implements Runnable{
        // 是否工作
        private volatile boolean running = true;
        @Override
        public void run() {
            while(running){
                Job job = null;
                synchronized (job){
                    // 如果工作者列表是空的、那么就wait
                    while(jobs.isEmpty()){
                        try {
                            jobs.wait();
                        } catch (InterruptedException e) {
                            // 感知到外部对WorkerThread的中断操作、返回
                            Thread.currentThread().interrupt();
                            return;
                        }
                    }
                    jobs.removeFirst();
                }

                if(job != null){
                    try {
                        job.run();
                    } catch (Exception e) {
                       // 忽略执行中的Exception
                    }

                }
            }
        }

        private void shutDown(){
            running = false;
        }
    }
}
